BAGHDAD -- In front of a blue metal gate, women in black abayas clutch food ration cards and exhibit a confidence rarely felt in the Iraqi capital. They will feed their families tonight. Several yards away, men sit behind wooden desks poring over hundreds of colorful folders, one each for Shiite families forced to flee their homes. Every family will be given a new life.

This busy office in the heart of the vast Shiite slum of Sadr City is not an arm of the government of Prime Minister Nouri al-Maliki. Nor is it a relief agency. It is the domain of the 33-year-old Shiite cleric Moqtada al-Sadr. Here, Sadr doles out aid to his neediest followers, from cradle to grave, filling a void in a desperately uncertain country.

"We get no help from Maliki. Only Sayyid Moqtada helps us," said Saleh al-Ghathbawi, a tall, balding clerk in a blue tracksuit, using the honorific that signifies Sadr's descent from the prophet Muhammad.

As the United States and Iraq proceed with a six-week-old security offensive to pacify the capital, Sadr's black-clad fighters have melted away. His advisers have fled to evade arrest. His own whereabouts are contested. U.S. intelligence officials say elements of his Mahdi Army militia have splintered off beyond his control.

Yet nowhere is Sadr's power more visible than in the sprawling district in eastern Baghdad that bears his family's name. Through legacy, symbolism and money, he has built up his street credentials by helping and protecting Iraq's Shiite majority. His militiamen have made Sadr City into the safest, most homogenous enclave in a capital scarred by war and ruled by a fragile government. It often appears to operate like a separate nation, where Sadr's words carry the weight of law.

The cleric's influence is everywhere. His representatives run the hospitals, the Islamic courts, the police, the municipal offices and the mosques. He pays for funerals and school books. He builds houses and controls inflation. He punishes the corrupt and those whose activities taint Islam or his privileged name.

"He is our marja," said Adil Murad Ali Muhammad, a retired civil servant in a gray jacket, referring to a supreme authority on Shiite religion and law.

Revitalizing his city, Sadr representatives say, is a key motive behind the cleric's uneasy cooperation with his arch adversary, the U.S. military, in recent weeks. Several reconstruction projects, some U.S.-funded, are already underway.

"We've asked the Americans to work in Sadr City responsibly, rationally and wisely," the district's mayor, Rahim al-Darraji, said this month. "Because Sadr City represents the determination and resilience of Iraq."

With a population of about 2 million people, Sadr City is the source of Sadr's political and religious clout. That, in turn, is pivotal to the future of his community, which he hopes to represent long after U.S. troops are gone. To understand Sadr's ambitions is to understand his relationship to his city and its residents.

An Atmosphere of Trust

At one entrance into Sadr City, a banner reads: "Enter it safely. The illuminated Sadr City."